Stirrup structure



FIG. 1 is a front view of the stirrup structure;

FIG. 2 is a rear view of the stirrup structure;

FIG. 3 is a top view of the stirrup structure;

FIG. 4 is a bottom view of the stirrup structure;

FIG. 5 is a right side view of the stirrup structure;

FIG. 6 is a left side view of the stirrup structure;

FIG. 7 is a perspective view of the stirrup structure; and,

FIG. 8 is a perspective view of the stirrup structure in use, the broken lines representing beams which are included for the purpose of illustrating environmental structure and form no part of the claimed design. 

CLAIM The ornamental design for a stirrup structure, as shown and described. 